The present invention relates to subterranean treatment fluids. More particularly, the present invention relates to low-viscosity subterranean treatment fluids with proppants suspended in gel fragments and methods of use thereof.
Fracturing (e.g., hydraulic fracturing) is a technique in which fractures are propagated in a rock layer by the introduction of a pressurized fluid. Often, fracturing operations are performed for the purpose of extracting certain fluids such as petroleum, natural gas, coal seam gas, and the like. Hydraulic fracturing can be used to increase or restore the rate at which such fluids can be produced from a subterranean formation.
Hydraulic fracturing often requires the use of fracturing fluids that have been viscosified. Increasing the viscosity of a fluid increases its ability to transport solids, such as proppant. Proppant acts to maintain the integrity of created fractures such that the fracture does not completely close once the fracturing pressure is released. A sufficiently high viscosity is needed to retain the proppant particulates in suspension in order to transport proppants while reducing the tendency of the proppant to settle out of the fracturing fluid before reaching the desire placement zone.
Fracturing fluids are often viscosified by gelling agents such as polysaccharides (e.g., guar gums, cellulose derivatives, etc.), biopolymers, synthetic polymers, and/or derivatives thereof to form crosslinked gels. The exact viscosities required in conventional fracturing fluids may be context dependent (e.g., formation temperature) but are generally well-known or may be ascertained by those of ordinary skill in the relevant art.
Fracturing fluid also may be used as a carrier fluid, for example, in gravel packing techniques. Gravel packing is a technique used to control formation during downhole operations. In gravel packing operations, a screen is placed in a subterranean formation across a productive interval and sand suspended in carrier fluid is pumped into the formation to fill the annular space between the screen and the formation. In some cases, an operator may choose to combine the processes of hydraulic fracturing and gravel packing into a unified treatment that can stimulate production while providing an annular gravel pack for sand control (“frac packing operations”).
Once the fracturing fluid has delivered proppant to the fracture or delivered sand in gravel packing or frac packing operations, it is often desirable to lower the viscosity of the fracturing fluid such that the fluid can be recovered from the formation using minimal energy. The removal of the spent fracturing fluids from the subterranean formation is typically required to allow hydrocarbon production. This reduction in viscosity of the fracturing fluid is often achieved using a breaker that breaks the cross-linking bonds of the crosslinked gels.
Despite the widespread use of hydraulic fracturing in the recovery of hydrocarbons and natural gas, conventional fracturing fluids and techniques may have several limitations. As described earlier, conventional proppant-laden fracturing fluids are often viscosified and crosslinked, which requires the use of relatively high horsepower in order to pump and transport the proppant-laden fluid down to the target site. Conventional fracturing fluids may also suffer from fluid leakoff problems. For example, over 70% of the injected volume may leakoff during conventional fracturing. Furthermore, conventional techniques for lowering viscosities (“breaking”) of fracturing fluids can be unreliable and sometimes results in incomplete and/or premature breaking of the fluid.